The present invention relates to automatic locking seat belt retractors of the type in which the belt is wound on a spring-actuated spool which exerts a constant retracting force on the belt while allowing the belt to be extended by manually pulling it off the spool, in which means are provided for locking the belt against further extension at any desired degree of extension by locking it against unwinding rotation. The present invention is an improvement over the automatic seat belt retractor shown in U.S. Pat. No. 3,667,698.
The seat belt retractor which is the subject matter of U.S. Pat. No. 3,667,698 has proven to be very reliable and satisfactory and has achieved wide-spread commercial acceptance in the automobile industry. In the seat belt retractor disclosed in that patent, the locking action consists of a pawl that is normally biased to an engaged position with a ratchet to prevent unwinding rotation of the spool. The retractor has a clutch which is journaled concentrically with the spool for limited rotation with the spool through a frictional driving connection with the spool. The clutch is driven to one limit of its movement by initial extension of the seat belt and in that position holds the pawl out of engagement during further extension. Initial retracting movement at any degree of extension moves the clutch to a position in which it allows pawl engagement, thereby locking the belt against extension due to a subsequent protraction. The retractor also includes secondary means for unlocking the pawl and holding it in the unlocked condition automatically when the belt is subsequently fully retracted. The secondary means is driven by the spool and is effective to hold the pawl out of engagement when the belt is fully retracted and during a limited initial extension from the fully retracted position.
Due to the frictional forces necessary to operate the patented seat belt retractor, a relatively heavy return spring is required on the spool. Thus, protraction of the belt is relatively difficult and an uncomfortably strong bias is placed on the lap of the user.
Accordingly, an object of the present invention is to provide an improved automatic locking seat belt retractor which is an improvement over the seat belt retractor shown in U.S. Pat. No. 3,667,698.
Another object of the present invention is to provide a seat belt retractor which permits protraction of the belt by a relatively light force.
A further object of the present invention is to provide an improved locking seat belt retractor which does not utilize a clutch.
Still another object of the present invention is to provide an improved seat belt retractor having a minimum of parts.
The foregoing and other objects are achieved according to the present invention by employing a relatively light spring which exerts a constant relatively light belt retracting force. A pawl and ratchet assembly are provided for locking the belt against further extension at any desired degree of extension. An indexing finger is attached to the pawl, a free end of which is in contact with a grooved plate attached to and rotatable with the spool. The grooved plate has a number of grooves set in specific patterns thereon for locating and guiding the indexing finger into appropriate positions according to the degree of protraction or retraction of the seat belt. The position of the indexing finger on the grooved plate in turn sets the pawl in a specified position relative to the ratchet. At certain positions of the indexing finger on the grooved plate, the pawl is moved into engagement with the ratchet thereby locking the seat belt against further extension.
Other objects, advantages and features of the invention will become apparent from the following description taken in conjunction with the accompanying drawings.